The entire disclosure of Japanese Patent Application No. 2006-200400, filed Jul. 24, 2006 is expressly incorporated herein by reference.
1. Technical Field
The present invention relates to a liquid ejecting apparatus. More specifically, the present invention relates to a liquid ejecting apparatus capable of securely capping the liquid ejecting nozzles in a inexpensive and secure manner.
2. Related Art
One example of a liquid ejecting apparatuses which eject liquid onto a target is an ink jet recording apparatus which records print data onto a recording sheet by ejecting ink droplets from nozzles onto the recording sheet. In such apparatuses, however, many printing defects may occur, such as increased ink viscosity caused by evaporation of solvents from the openings of the nozzles, dust adhesion in the openings of the nozzles, and the mixing of bubbles in the ink caused by replacement of a cartridge, and the like.
In order to ensure that the nozzles are operating properly, a cap for capping the nozzle faces is typically used to cover the nozzle faces of the recording head when the apparatus is not printing. An ink absorber is placed inside the cap to keep the humidity inside the cap high during capping in order to prevent evaporation of the solvent through the nozzle openings, in an attempt to prevent the increase in the viscosity of ink.
In addition, an exhaust port is formed in the bottom surface of the cap to discharge ink or bubbles which is connected to a tube fixed to the cap. A suction pump is attached to the tube, and a negative pressure is applied to the inside of the cap by a suction operation of the suction pump. A cleaning operation is also performed by discharging any ink with an increased viscosity or bubbles caused by the replacement of the ink cartridge.
A cleaning device has been developed, which includes a plurality of recording heads and a plurality of caps covering the recording heads, wherein a suction operation may be performed individually or collectively on the recording heads. In such a cleaning device, a negative pressure supply switching unit is provided which selectively switches the supply of negative pressure to the caps. When the negative pressure supply switching unit selects a cap, the supply of negative pressure and the suction pump is driven, such that negative pressure is supplied to the cap connected to the suction pump, causing a suction operation to be performed on the recording head corresponding to the cap. With this arrangement, it is possible to selectively perform a suction operation on the caps.
One example of an apparatus which performs a suction operation on the caps is disclosed in Japanese Patent Application JP-A-2001-347689, which discloses an apparatus wherein the supply of negative pressure is selected by the phase control of a rotating cam. The rotating cam serves as a negative pressure supply switching unit that selectively presses and blocks the tubes in communication with the caps. Moreover, Japanese Patent Application JP-A-2004-358792 discloses an apparatus in which a cap is selected by a valve operation, and Japanese Patent Application JP-A-2005-329693 discloses an apparatus wherein the cap is selected by a cylindrical cam-based valve operation.
One difficulty in the apparatus in which the cap is selected using the phase control of the rotating cam, is that it is necessary to have a motor for driving the rotating cam as well as a sensor for detecting the phase of the rotating cam, meaning that the cost of the apparatus is increased. And in the apparatuses where the cap is selected by the valve operation, it is necessary to have a complex mechanism such as a valve in the ink flow path, which increases the likelihood of clogging when using pigment ink, which is undesirable in view of long term reliability.